N, M = map(int, input().split())
S = [True for _ in range(N)]
for _ in range(M):
    a, b = map(int, input().split())
    S[a] = not(S[a]) 
    S[b] = not(S[b]) 
count = 0
for s in S:
    if not s:
        count += 1
print('YES' if count <= 2 else 'NO')